The present invention is directed to an energy absorbing device, and more specifically, to a fluid-mechanical shock absorber for use with an automobile bumper.
The conventional automobile bumper has been proven to be notoriously ineffective in preventing substantial damage to automobile body components, such as the grill, trunk lid and fenders. Numerous attempts have been made over the years to provide a stronger bumper but a strong bumper per se is relatively useless unless it is mounted on the frame with the interposition of adequate shock absorbing devices.
The U.S. patent to Moyer (U.S. Pat. No. 4,823,923) discloses an energy dampening apparatus for use between the frame of an automobile body and the bumper. Sudden impacts are dissipated through the sequential sheering of rods or pins anchored perpendicularly to the incoming force and through the compression and evacuation of gel through holes or valves in a cylinder. By varying the diameter and length of the cylinder, pistons and the number, size and composition of sheer pins, the number and size of restriction holes and the amount of gel, the system will dissipate impacts within predetermined limits. However, the sheer pins in any given embodiment are identical and the holes through which the gel is extruded are all of equal size. Accordingly, as the energy dampening apparatus is compressed in length, there is no sequential increase in the resistance provided against further compression.
The U.S. Patent to Lohr et al. (U.S. Pat. No. 4,641,872) discloses a collision damper having a damping piston and a deformable tube connected thereto. Upon movement of the deformation tube upon impact to an automobile bumper or the like, the fluid within a chamber will be forced through a throttle opening into a second fluid chamber whereby the increased fluid pressure in the second chamber will force a piston to move and compress a gas within a gas chamber. If the force is great enough, the deformation tube will also be deformed along predetermined weak spots. Although a sequential dampening affect is achieved, there is no disclosure of providing a plurality of weak spots of varying strengths which will rupture in sequence upon the application of pressure to a fluid within the cylinder.
The U.S. patent to Harano (U.S. Pat. No. 4,190,276) discloses a deformable impact absorbing device for vehicles which may be mounted between the frame of the vehicle and the vehicle bumper. The device is comprised of a tapered polyhedral having a plurality of side cut-outs with the upper and lower edges of the cut-outs protruding outwardly and inwardly respectively from the side wall. Upon application of an axially directed force to the body, the body will undergo a sequential collapse.
The U.S. patent to Keeler (U.S. Pat. No. 4,257,581) discloses an impact absorbing strut for interconnecting the chassis and bumper of a motor vehicle. Keeler discloses an impact absorbing strut comprised of at least two telescoping tubes defining a damping fluid chamber. A solid piston is slidably mounted in the first fluid filled chamber and upon axial movement, the fluid will be pressurized. In one embodiment, a blow-out plug is provided which will be forced out of the end of the chamber upon an increase in the fluid pressure, whereby the fluid will be discharged. In other embodiments, each sequential fluid filled chamber is provided with an opening in the bottom end through which the fluid is expelled from one chamber to another to provide a sequential dampening effect.
The U.S. patent to Mitchell (U.S. Pat. No. 3,200,584) is directed to a sheer slide cushion wherein a sheer slide or piston is slidably mounted within a combustion chamber of a rocket engine. A plurality of spaced propellant inlet ports are provided which are sealed by sheer cups supported by and mounted in recesses of the sheer slide. A composite cushion is provided between complementary shoulders on the piston and cylinder. Upon ignition of the rocket engine, the sheer slide will be moved to crush a middle band in the composite cushion. Although the sheer cups will be sheered off upon relative movement between the piston and the cylinder, the primary purpose of the sheer cups is simply to allow communication between inlet ports and ports in the slide and do not have any relation to the cushioning which is accomplished solely by the composite cushion between the piston and the cylinder. Furthermore, all of the sheer cups are sheered simultaneously.